Nitropolystyrene



United States Patent No Drawing. Filed May 7, 1964, Ser. No. 365,794 4Claims. (Cl. 260-644) This application is a continuation-in-part ofapplication Serial No. 155,498 filed by us on November 28, 1961, forNitropolystyrene, now US. Patent No. 3,154,448.

The invention relates to nitropolystyrene.

The invention comprises, more particularly, nitrated atactic polystyreneof relatively low molecular weight or nitrated isotactic polystyrenes.

These compounds are useful as explosives of velocity of detonation thatlies in a range hereto not supplied, e.g., about 1,0002,000 m./sec. forthe dinitro compounds. This is far above that of standard explosivemixtures of combustible and oxidizing components such as black powder(about 400 m.) but far below the velocity of TNT and likenitroexplosives (4,0008,000 m.). For a given degree of nitration, on theother hand, the explosive force of nitropolystyrene is strong ascompared, for instance, with nitrated toluene. Thus ourdinitropolystyrene in the metal plate test for brisance gives, per unitof weight, a penetration equal to or in excess of that given bytrinitrotoluene.

Our dinitropolystyrene melts above about 260 C., if at all, as comparedwith melting temperatures within the range about 52-70 C. for thedinitrotoluenes and 80-l12 C. for the various isomeric trinitrotoluenes.

The nitrated polystyrene, either alone or compounded, may be formed intoblocks, i.e., shape retaining plasticbonded explosives that can bemolded into variously formed masses to fit spaces in which the explosiveis to be set and then fired. Such are the recesses in rivets that are tobe expanded by firing explosive in the said recesses.

As to materials, we obtain particularly satisfactory results includinghigh density, causing more of the explosive to be insertable into agiven drill hole or other space, when we use isotactic polystyrene asthe material to be nitrated. We may use also for most purposes, theproduct of nitration of atactic polystyrene of such relatively lowmolecular weight that the product, after the nitration will be belowabout 50,000. The polystyrene recommended for making such product is ofmolecular weight not substantially above about 80,000 before thenitration. Either of the polystyrenes after nitration and purificationby washing may be blended with a nitrated C -C polyol plasticizer as,for example, nitroglycerine of dynamite grade, monoor dinitroglycol, ordinitropentaerythritol in the proportion of -50 parts for 100 of thenitrated polystyrene.

A convenient acid for nitrating the polystyrene is mixed nitric andsulfuric acids with substantial sulfur triox de content. Such mixed acidis obviously anhydrous. We nitrate to an average nitrogen contentcorresponding approximately to monoor dinitropolystyrene, the latterhaving two N0 groups for each monomeric styrene unit (wt. 104)represented in the polymer.

As the stabilizer to decrease the autocatalytic decomposition of thenitropolystyrene, if desired, we use one of the organic acceptors ofacid so as to reduce the pH that otherwise would result as acid isliberated by slow de composition. Examples of such acceptors to be usedare nitrogen bases, that is, salt formers with acids such asdiphenylamine, tetramethylaniline, and urea. The stabilizer is used toadvantage in the amount of about 0.1-2 parts for 100 parts of thenitropolystyrene.

As a component, it any, to modify the explosive properties of thenitropolystyrene, we may use the ammonium nitrate, sodium or potassiumnitrate, trinitrotoluene or the like within the range 50500 parts for100 parts of the nitropolystyrene.

The components may be simply admixed but for many purposes, such asexplosive blocks, should be bonded by the thermoplasticnitropolystyrene'iinto a firm, shape retaining mass.

The invention will be further illustrated by description in connectionwith the following specific examples of the practice of it. In theseexamples and elsewhere herein proportions are expressed as parts byweight.

Example 1 Dinitro-isotactic-polystyrene is made as follows:

Fifty parts of isotactic polystyrene, made as described by Natta in DieMakromalekulare Chemie, vol. 16, pp. 213-237 (1955), and elsewhere, isgradually added with stirring to an anhydrous mixture of 450 parts ofnitric acid of specific gravity 1.50, 200 parts of sulfuric acid of sp.gr. 1.84 and 100 parts of sulfur trioxide, the latter being dissolved inadvance in the sulfuric acid. The temperature of the mixing during theintroduction and solution of the polystyrene is maintained at 15 -20 C.by external cooling. After all of the polystyrene has been introducedand dissolved, the temperature is raised to 5055 C. and kept within thatrange for 2 hours, i.e., until the reaction that has followed the mixingis substantially completed.

The resulting mixture of nitro-isotactic-polystyrene and spent acids iscooled to 25 C. and poured into approximately 5,000 parts of cold Water.This precipitate, the nitropolystyrene, is separated from the aqueousphase by decantation, washed with cold water to remove acid. and finallywith a dilute solution of sodium carbonate and ammonium hydroxide untilthe washings are not acidic to Congo red.

The product is dried at C., to a firm hard relatively dense solid.Stabilizers are not necessary for the nitrated isotactic product. Thestabilizers and/or other compounding ingredients shown herein may beadmixed, however, as in the proportion of 0.5 part of the stabilizer and200 parts of ammonium nitrate or TNT component for parts of thenitropolystyrene.

Example 2 The procedure and compositions of Example 1 are used exceptthat the polystyrene used for the nitration is the commercial atacticpolystyrene of molecular weight about 80,000. The yield of the washedand dried product is 70 parts or 99.5% of theory on the basis of thepolystyrene used.

The product starts to decompose on heating gradually at 260 C. and isnot fully melted at temperatures as high as 300 C. The nitrogen contentis 14.2%. The theory is 14.3% for dinitropolystyrene having 2 N0 groupsfor each monomeric styrene unit.

. Overall Depth of Explosive Density of Penetration,

Explosive, g. inch per ml.

Dinitropolystyrene 0. 65 0. 145 Do 0. 67 0. 153 Trinitrotoluenm- 0.95 0.194

Corrected for its lower density, the dinitropolystyrene explosive on anequal weight basis shows a calculated brisance, as indicated by thedepth of penetration, at least approximately equal to that of the morehighly nitrated trinitrotoluene. I

In spite of the high brisance, the dinitropolystyrene has a relativelylow velocity of detonation, about 1,000-2000 meters per second, ascompared to about 4,700 for TNT at a density of 0.95 g./ml. This ratefor our product adapts it especially for dispersing, to the rightdegree, materials mixed therewith that are to be disseminated into air.

Example 3 The procedure and composition of Example 2 are used exceptthat the washed and dried dinitropolystyrene is mixed with 0.5 %1% ofits Weight of each of the following stabilizers used separately and inturn: diphenylamine, tetramethylaniline and urea, to retard developmentof instability on storage.

Example 4 The procedure and composition of Example 2 are used exceptthat the washed and dried nitropolystyrene is parts of sodium nitrateand potassium nitrate used separately and in turn. The nitrate usedsupplies available oxygen during the explosion of the composition andthus promotes combustion to the stage of increased energy release andless smoking.

Example 5 The procedure and composition of Example 3 are used exceptthat the washed and dried dinitropolystyrene is mixed thoroughly and inthe amount of 100 parts with 500 parts of ammonium nitrate. The ammoniumnitrate provides oxygen for the more nearly complete combustion of thedinitropolystyrene and also its own powerful explosive force.

It will be understood that it is intended to cover all changes andmodifications of the examples of the invention herein chosen for thepurpose of illustration which do not constitute departures from thespirit and scope of the invention.

We claim:

1. A compound selected from the group consisting of nitrated atacticpolystyrene of average molecular weight below about 50,000 afternitration and nitrated isotactic polystyrene, the compound being anexplosive of brisance on detonation approximately equal at least to thatof TNT and of velocity of detonation not above about half that of TNT.

2. As an explosive, dinitro-isotactic-polystyrene.

3. As an explosive, dinitro-atactic-polystyrene of average molecularweight below about 50,000.

4. The process of nitrating polystyrene which includes maintaining thepolystyrene in contact with an anhydrous solution of nitric acid,sulfuric acid and sulfur trioxide until the reaction that ensues iscompleted, then adding water to precipitate the resultingnitropolystyrene and washing the precipitated product to remove acidther from.

References Cited by the Examiner UNITED STATES PATENTS 2,572,420 10/51Zenftman et al. 149-105 X CARL D. QUARFORTH, Primary Examiner.

1. A COMOUND SELECTED FROM THE GROUP CONSISTING OF NITRATED ATACTIC POLYSTYRENE OF AVERAGE MOLECULAR WEIGHT BELOW ABOUT 50,000 AFTER NITRATIONAND NITRATED ISOTACTIC POLYSTYRENE, THE COMPOUND BEING AN EXPLOSIVE OF BRISANCE ON DETONATION APPOXIMATELY EQUAL AT LEEAST TO THAT OF TNT AND OF VELOCITY OF DETONATION NOT ABOVE ABOUT HALF THAT OF TNT. 